<head>
	<meta charset="UTF-8">
	<title>Title</title>
	<style type="text/css">
		* {
			padding: 0;
			margin: 0;
		}
		
		li {
			list-style: none;
		}
		
		body {
			background: #940032;
		}
		
		#counter {
			width: 500px;
			height: 420px;
			background: #939;
			margin: 50px auto 0;
			position: relative;
		}
		
		#counter h2 {
			line-height: 42px;
			padding-left: 15px;
			font-size: 14px;
			font-family: arial;
			color: #ff3333;
		}
		
		#counter a {
			font-weight: normal;
			text-decoration: none;
			color: #ff3333;
		}
		
		#counter a:hover {
			text-decoration: underline;
		}
		
		#bg {
			width: 280px;
			height: 200px;
			border: 3px solid #680023;
			background: #990033;
			filter: alpha(opacity=80);
			opacity: 0.8;
			position: absolute;
			left: 50%;
			top: 115px;
			margin-left: -141px;
		}
		
		#counter_content {
			width: 250px;
			position: absolute;
			top: 130px;
			left: 130px;
			z-index: 1;
		}
		
		#counter_content h3 {
			margin-bottom: 10px;
		}
		
		#counter_content h3 input {
			border: none;
			width: 223px;
			height: 30px;
			line-height: 30px;
			padding: 0 10px;
			background: url(img/ico.png) no-repeat;
			text-align: right;
			color: #333;
			font-size: 14px;
			font-weight: bold;
		}
		
		#counter_content div {
			width: 250px;
		}
		
		#counter_content input {
			width: 60px;
			height: 30px;
			line-height: 30px;
			float: left;
			background: url(img/ico.png) no-repeat -303px 0;
			text-align: center;
			color: #fff;
			cursor: pointer;
			margin: 0 1px 4px 0;
			border: 0;
		}
		
		#counter_content div>input:hover {
			background: url(img/ico.png) no-repeat -243px 0;
		}
		
		#counter p {
			width: 500px;
			position: absolute;
			bottom: 20px;
			left: 0;
			color: #ff3333;
			text-align: center;
			font-size: 12px;
		}
	</style>
</head>

<body>
	<div id="counter">
		<h2>简易计算</h2>
		<div id="counter_content">
			<h3><input id="input1" type="text" value="0"/></h3>
			<div id="div1">
				<input type="button" value="7" onclick="kick('7')" />
				<input type="button" value="8" onclick="kick('8')" />
				<input type="button" value="9" onclick="kick('9')" />
				<input type="button" value="+" onclick="kick('+')" />
				<input type="button" value="4" onclick="kick('4')" />
				<input type="button" value="5" onclick="kick('5')" />
				<input type="button" value="6" onclick="kick('6')" />
				<input type="button" value="-" onclick="kick('-')" />
				<input type="button" value="1" onclick="kick('1')" />
				<input type="button" value="2" onclick="kick('2')" />
				<input type="button" value="3" onclick="kick('3')" />
				<input type="button" value="*" onclick="kick('*')" />
				<input type="button" value="0" onclick="kick('0')" />
				<input type="button" value="C" onclick="kick('C')" />
				<input type="button" value="=" onclick="kick('=')" />
				<input type="button" value="/" onclick="kick('/')" />
			</div>
		</div>
	</div>
</body>
<script>
	var showInput = document.getElementById("input1");
	var isClear = false;
	var tempStr = "";
	var clacType = "";
	var isContinue = true;

	function kick(clickValue) {
		switch(clickValue) {
			case "=":
				if(tempStr != "" && clacType != "") {
					showInput.value = clac(tempStr, showInput.value, clacType);
					isContinue = false;
					clacType = "";
				}
				break;
			case "+":
			case "-":
			case "*":
			case "/":
				//如果预存的操作符不为空 表示表示连续操作
				if(clacType != "" && !isContinue) { //先执行计算
					tempStr = clac(tempStr, showInput.value, clacType);
					isClear = true;
					clacType = clickValue;
				} else {
					tempStr = showInput.value; //点击操作符之后 预存字符
					isClear = true; //表示点击了操作符
					clacType = clickValue; //预存操作符
				}
				isContinue = true;
				break;
			case "C":
				showInput.value = "0";
				isClear = false;
				tempStr = "";
				clacType = "";
				break;
			default: //普通的数字按钮点击
				showInput.value = showInput.value == "0" ? "" : showInput.value;
				isContinue = false;
				if(isClear) {
					showInput.value = "";
					showInput.value += clickValue;
					isClear = false;
				} else {
					showInput.value += clickValue;
				}
				break;
		}
	}

	function clac(num1, num2, type) {
		switch(type) {
			case "+":
				return Number(num1) + Number(num2);
			case "-":
				return Number(num1) - Number(num2);
			case "*":
				return Number(num1) * Number(num2);
			case "/":
				return Number(num1) / Number(num2);
			default:
				break;
		}
	}
</script>